8027890 li eds 04 wastewater treatment v7 en - festo · pdf file1.1.2 piping and...

Festo Didactic

8027890 en

12/2013 R1.0

Wastewater treatment

EDS®

Water Management

Workbook

With CD-ROM

Order No.: 8027890

Status: 12/2013

Author: Martina Groß, Christian Klippstein*, Peter Maurer*, Yvonne Salazar,

Thomas Schwab**, Kevin Treffry-Goatley***, James Voortman***

Graphics: Doris Schwarzenberger

Layout: 01/2014, Frank Ebel

© Festo Didactic GmbH & Co. KG, 73770 Denkendorf, Germany, 2014

Internet: www.festo-didactic.com

E-mail: [email protected]

* Stuttgart University

Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA)

Bandtäle 2

70569 Stuttgart

Federal Republic of Germany

** ADIRO Automatisierungstechnik GmbH

Limburgstrasse 40

73734 Esslingen

Federal Republic of Germany

** The Water Academy

P O Box 355

Knysna 6570

South Africa

The purchaser shall receive a single right of use which is non-exclusive, non-time-limited and limited

geographically to use at the purchaser's site/location as follows.

The purchaser shall be entitled to use the work to train his/her staff at the purchaser's site/location and

shall also be entitled to use parts of the copyright material as the basis for the production of his/her own

training documentation for the training of his/her staff at the purchaser's site/location with

acknowledgement of source and to make copies for this purpose. In the case of schools/technical colleges

and training centres, the right of use shall also include use by school and college students and trainees at

the purchaser's site/location for teaching purposes.

The right of use shall in all cases exclude the right to publish the copyright material or to make this available

for use on intranet, Internet and LMS platforms and databases such as Moodle, which allow access by a

wide variety of users, including those outside of the purchaser's site/location.

Entitlement to other rights relating to reproductions, copies, adaptations, translations, microfilming and

transfer to and storage and processing in electronic systems, no matter whether in whole or in part, shall

require the prior consent of Festo Didactic GmbH & Co. KG.

© Festo Didactic GmbH & Co. KG 8027890 III

Contents

EDS® Water Management __________________________________________________________________ V

Description ______________________________________________________________________________ V

EDS® systems data ________________________________________________________________________ VI

The four systems of the EDS® Water Management _____________________________________________ VII

Piping and instrumentation diagrams ________________________________________________________ VIII

Correlating the exercises with the EDS® Water Management systems _______________________________ IX

Appropriate use and disclaimer ____________________________________________________________ XII

Notes for the trainer/instructor _____________________________________________________________ XIII

Structure of the exercises _________________________________________________________________ XIII

Exercises and solutions

1 Wastewater treatment _______________________________________________________________ 3

1.1 The training equipment ______________________________________________________________ 3

1.1.1 System data _______________________________________________________________________ 3

1.1.2 Piping and instrumentation diagram of the Wastewater Treatment System ____________________ 4

1.2 The most important P&I symbols used for the EDS® Water Management ______________________ 4

1.3 Learning outcomes correlated with exercises _____________________________________________ 6

1.4 Introduction to the learning module “Wastewater treatment” _______________________________ 7

1.4.1 Pre-treatment ______________________________________________________________________ 7

1.4.2 Primary Treatment __________________________________________________________________ 8

1.4.3 Secondary or biological treatment ______________________________________________________ 8

1.4.4 Tertiary treatment ___________________________________________________________________ 9

2 Sedimentation ___________________________________________________________________ 10

2.1 Fundamentals ____________________________________________________________________ 10

2.1.1 How sedimentation works __________________________________________________________ 10

2.1.2 Important process parameter _______________________________________________________ 10

2.1.3 Zones of a sedimentation tank (settling tank) __________________________________________ 11

2.1.4 Types of clarifiers _________________________________________________________________ 13

2.1.5 Tank construction _________________________________________________________________ 14

2.1.6 General problems with all types of clarifiers ____________________________________________ 15

2.1.7 Sludge formation and removal _______________________________________________________ 16

2.1.8 Operating the clarifier______________________________________________________________ 22

2.1.9 Sludge withdrawal systems _________________________________________________________ 23

Contents

IV © Festo Didactic GmbH & Co. KG 8027890

2.2 Exercises ________________________________________________________________________ 25

2.2.1 Analysis of factors affecting sedimentation ____________________________________________ 25

2.2.2 Simulation of the sedimentation of sludge (granulate) ___________________________________ 29

2.2.3 Analysis of flow rates ______________________________________________________________ 31

2.2.4 Influence of solids load on sedimentation _____________________________________________ 33

3 Biological treatment (activated sludge) ______________________________________________ 34

3.1 Fundamentals ____________________________________________________________________ 34

3.1.1 Aerobic wastewater treatment _______________________________________________________ 34

3.1.2 Terms to characterize the activated sludge process ______________________________________ 36

3.2 Exercises ________________________________________________________________________ 37

3.2.1 Keeping a high solids concentration in the aeration tank _________________________________ 37

3.2.2 Aeration _________________________________________________________________________ 41

Appendix ______________________________________________________________________________ 48

Safety instructions _______________________________________________________________________ 48

Components ____________________________________________________________________________ 50

Abbreviations ___________________________________________________________________________ 53

© Festo Didactic GmbH & Co. KG 8027890 V

EDS® Water Management

Description

The EDS® (Environmental Discovery System) Water Management is designed to simulate the entire cycle of

human water use. This starts with water catchment by pumping from groundwater, springs or surface water

and includes subsequent storage and purification. It also covers the distribution of water to consumers and

its use – which causes water to become wastewater. Further on wastewater transport together with rain

runoffs and wastewater treatment are reproduced.

In a real wastewater treatment plant the final effluent is discharged into surface water, normally rivers.

Direct reuse is not common, but the effluent now is part of natural water bodies which again feeds the

sources of water extraction. The water cycle in the EDS® Water Management is completed by reusing the

final effluent as input water into the system.

The EDS® Water Management training equipment vividly simulates this “man-made” water cycle with its

four systems:

1. Water Treatment

2. Water Supply

3. Wastewater Disposal

4. Wastewater Treatment

Processes such as pumping, storage, flocculation, disinfection and distribution of water can be learnt

through practical exercises. After adding solid matter, we follow the stream of wastewater and discover

processes such as sedimentation, aeration and sludge recirculation.

Comprehensive documentation with theoretical input additionally promotes the learning success. Four of

the workbooks correspond directly to the systems, whereas two overarching workbooks additionally deliver

a sound introduction into closed-loop control technology and energy efficiency.

The following workbooks are available:

1. Water treatment

2. Water supply

3. Wastewater disposal

4. Wastewater treatment

5. Monitoring, controlling and optimising operations

6. Energy optimisation in water and wastewater treatment plants

Each system can be used as stand-alone training equipment for an individual learning module. The training

equipment can be modified individually as piping and sensors use are flexible. If the four systems are

connected they form an integrated training equipment that covers all of the processes and exercises

described in the workbooks. Using the systems together allows students to see how individual process

steps interact as well as how a measure taken in one area affects one or more of the other systems.


VI © Festo Didactic GmbH & Co. KG 8027890

As in the real world, the processes interact. The wastewater treatment plant, for example, has to process the

amount and composition of wastewater delivered by the sewer system. Similarly, the single systems of the

training equipment are connected by pipes which transport the water, whereas the control process is

separate for each system. So the EDS® Water Management invites students to ‘try things out’ and even

simulate problems, using different settings and system states. This experimentation can be done without

incurring costs or causing damage, something not possible in a real water or wastewater treatment plant.

After completion of the learning modules described in the workbooks, the student’s expertise will be

significantly increased. The strong practical orientation helps to transfer the knowledge and skills acquired

during the training directly to their work environment. Professional training actively contributes to safe and

efficient operation of treatment plants and improves the availability of clean drinking water.

EDS® systems data

Dimensions of the EDS® Water Management without main storage tank, worktable and PC desk

Width: 2660 mm (minimum); 3500 mm (optimum)

Depth: 400 mm

Height: 1150 mm from table top

The EDS® Water Management training equipment with all four systems


© Festo Didactic GmbH & Co. KG 8027890 VII

The four systems of the EDS® Water Management

Water Treatment

The System has been designed for use in the learning modules:

Water treatment

Monitoring, controlling and optimising operations

Energy optimisation in water and wastewater treatment plants

Conducting the exercises on the Water Treatment System, students learn the principles, function and

operation of a variety of water purification processes. Subsequently, they apply the acquired skills to create

an environmentally safe effluent on one side and to ensure drinking water purification on the other side.

Water Supply

The system has been designed for use in the learning modules:

Water supply



As the system is used in three learning modules, its range of applications is wide and students perform

many exercises on it. The learning module “Water Supply” pumps are one of the main topics, other

exercises deal with control technologies in water transport to achieve the optimum distribution of drinking

water to the consumer. In addition, the flow of water from the source to the public is examined.

Wastewater Disposal


Wastewater disposal



Using the system in the learning module “Wastewater Disposal”, students are familiarised with control

technologies of wastewater removal and the related processes. The flow of wastewater from urban

settlements to the wastewater plant is examined.


VIII © Festo Didactic GmbH & Co. KG 8027890

Wastewater Treatment


Wastewater treatment



In the learning module “Wastewater Treatment”, the system is used to illustrate the principles of

wastewater treatment processes focused on sedimentation, biological treatment and sludge recirculation. In

learning module “Energy Optimisation” the system illustrates processes and measures related to energy

efficiency in the water and wastewater treatment, especially aeration. For the module “Monitoring,

controlling and optimising operations” the topics flow control, aeration and fill level control can be treated.

Piping and instrumentation diagrams

The Water Treatment system and the Water Supply system


© Festo Didactic GmbH & Co. KG 8027890 IX

The Wastewater Disposal system and the Wastewater Treatment system

Correlating the exercises with the EDS® Water Management systems

The table below shows which of the EDS® systems can be used for which exercise. The systems concerned

are marked with “X”. If there is no “X” in a line, the respective exercise is knowledge driven and none of the

EDS® systems is required. “(X)” means that it is possible to conduct the exercise with this system. However

the systems marked with “X” are to be preferred.

Correlation of the exercises with the EDS® Water Management systems

W-

PUR

W-

SUP

WW-

TRA

WW-

TRE

Getting started

The “Getting started” also includes exercises for the commissioning of electronic

sensors, pumps and valves.

X X X X

Workbook “Water treatment”

2. Precipitation and Flocculation

2.2.1 Iron flocculation using iron hydroxide X

3. Chlorine dosing and disinfection

3.2.1 Chlorine dosage and measurement of chlorine concentration X

W-PUR: Water Treatment System

W-SUP: Water Supply System

WW-TRA: Wastewater Disposal System

WW-TRE: Wastewater Treatment System


X © Festo Didactic GmbH & Co. KG 8027890


W-

PUR

W-

SUP

WW-

TRA

WW-

TRE

Workbook “Water supply”

3. Operation of pumps

3.2.1 Setting up the pump (X) X (X) (X)

3.2.2 Pressure measurement

X

3.2.3 Flow measurement X (X) X (X)

3.2.4 Controlling water supply using hand valves X (X) X (X)

4. Water transport to high tower

4.2.1 Control of the filling level while simultaneously withdrawing water

X

4.2.2 Manual control of the filling level using 2-way ball valve with pneumatic actuator

X

5. Water supply to different pressure zones

5.2.1 Simulation of two settlement zones located on different altitudes

(both systems are used)

X and X

6. Water loss

6.2.1 Identification of water loss

X

Workbook “Wastewater disposal”

2. Principles of water flow in pipes

2.2.1 Wastewater disposal in gravity sewers – Hydraulic capacity, impounding and

backwater

X

3. Transport of solids

3.2.1 Transport of solids in sewers with varying flow rates

X

4. Operation of sewer systems

4.2.1 Flow control simulating a rain overflow basin

X

4.2.2 Drain Control – closed loop control using the proportional media valve

X

Workbook “Wastewater treatment”

2. Sedimentation

2.2.1 Analysis of factors affecting sedimentation

2.2.2 Simulation of the sedimentation of sludge (granulate)

X

2.2.3 Analysis of flow rates

X

2.2.4 Influence of solids load on sedimentation

X

3. Biological treatment (activated sludge)

3.2.1 Keeping solids concentration in the aeration tank high

X

3.2.2 Aeration

X






© Festo Didactic GmbH & Co. KG 8027890 XI


W-

PUR

W-

SUP

WW-

TRA

WW-

TRE

Workbook “Monitoring, controlling and optimising operations”

2. Closed loop control technology: Pump

2.2.1 Controlling the fill level using a two-step controller

X

2.2.2 Controlling the fill level using a continuous controller

X

2.2.3 Flow control using a proportional-integral controller X X X

3. Closed loop control technology: Proportional media valve

3.2.1 Volumetric Flow Control

X

3.2.2 Drain Control

X

4. Closed loop control technology: Aeration

4.2.1 Controlling the oxygen concentration using a two-step controller

X

4.2.2 Controlling the oxygen concentration using a continuous controller

X

Workbook “Energy optimisation in water and wastewater treatment plants”

2. Energy consumption and power generation

2.2.1 Consumption of primary energy

2.2.2 Energy saving in daily life

2.2.3 Energy consumption in facilities for water- and wastewater treatment

2.2.4 Assessment of electrical energy consumption in a wastewater treatment plant

3. Forms of energy, efficiency and power

3.2.1 Examination of electrical energy consumption

of the EDS® Water Management X X X X

3.2.2 Forms of energy

3.2.3 Efficiency of the pump X X X X

3.2.4 Energy monitoring of the solenoid valve X X

X

4. Interference and water supply

4.2.1 Effects of interference in the piping system X X X X

5. Energy optimisation of pumping: closed-loop control

5.2.1 Optimising energy consumption in fill level control

X

5.2.2 Optimising flow control X X X






XII © Festo Didactic GmbH & Co. KG 8027890


W-

PUR

W-

SUP

WW-

TRA

WW-

TRE

6. Energy optimisation of aeration and costs

6.2.1 Energy consumption of the air blower at different power settings

X

6.2.2 Controlling the oxygen concentration using a two-step controller

X

6.2.3 Controlling the oxygen concentration using a continuous controller

X

6.2.4 Energy consumption of aeration

X

6.2.5 Calculation of aeration cost

7. Causes for waste of energy

7.2.1 Excessive energy consumption and counter measures

8. Energy management

8.2.1 Permanent control of the measures and energy optimisation

8.2.2 Cost optimisation

9. Energy generation in wastewater plants

9.2.1 Estimate the power generation



WW-TRP: Wastewater Disposal System


Appropriate use and disclaimer

The EDS® Water Management may only be used:

For its intended purpose in teaching and training applications

When its safety functions are in flawless condition

The components included in the training equipment have been designed in accordance with the latest

technology, as well as recognised safety rules. However, life and limb of the user and third parties may be

endangered, and the safe functioning of the components may be impaired, if they are used improperly.

The EDS® Water Management has been developed and manufactured exclusively for technical and

vocational education and training (TVET). The respective educational institutions and their instructors must

ensure that all students observe the safety precautions described in this workbook.

Festo Didactic hereby excludes any and all liability for damages suffered by students, the educational

institution and/or any third parties, which occur during use of the training equipment in situations which

serve any purpose other than education and training, unless such damages have been caused by Festo

Didactic due to malicious intent or gross negligence.


© Festo Didactic GmbH & Co. KG 8027890 XIII

Notes for the trainer/instructor

Please observe the specifications in the data sheets for the individual components carefully and in

particular all safety instructions in the previous chapter. Before the exercises are conducted, please

assess their possible hazards to avoid accidents and emergency situations.

Electrical components are pre-wired at the factory, and are mounted onto an H-rail for direct attachment

to the rectangular profile. Alternatively, they can be shipped unwired as a kit. In either case, wiring work

must only be carried out by qualified personnel.

Like all training products of Festo Didactic, the learning systems of the EDS® are strongly practice

focussed. Their prime objective is to increase the professional competence of students by giving them

tasks and challenges that reflect actual work conditions. During the training the instructor should

strictly focus on the learning outcomes and design the learning process in a way that at the end the

learning outcomes are achieved.

As the EDS® Water Management training equipment simulates real processes, it represents an ideal tool

to deliver relevant and state-of-the-art know-how and skills to students. Consequently, the conduction

of the exercises should form the core of the learning process. Theoretical explanations and

presentations should only be used to support the knowledge and skill transfer resulting from the

exercises.

Since the knowledge of students usually differs, the degree how in depth the contents of the learning

module should be treated might vary considerably. Thus, there is no concrete recommendation

concerning the duration of a learning module. Generally, the instructor should plan and conduct the

learning module in a way that the students have enough time to execute the exercises, ask questions

and share their experience and knowledge.

Structure of the exercises

The training equipment and workbooks of Festo Didactic facilitate a didactic approach that is oriented

towards hands-on learning. To support the practice-driven approach of the learning process, the exercises

play a crucial role. They reflect real work challenges and problems. Therefore it is important that they are

always explained in the context of work. Consequently, the exercises are composed of the following

structural elements:

Problem description

The problem description creates a scenario from the work place and places the students into a work

environment.

Layout

Sometimes an instruction is given on how to prepare an exercise, which materials are needed and how

to assemble the EDS® Water Management system that is used for the respective task(s).

Learning outcomes

The learning outcomes allow evaluating students’ learning success and giving employers an orientation

of the students’ competence level. Moreover they are guidelines for the learning process.


XIV © Festo Didactic GmbH & Co. KG 8027890

Tasks

Tasks contain a short and precise task description and give a clear explanation of what has to be done,

to be solved or achieved.

Training notes

Training notes give additional tips or information that help the students to successfully work on the

tasks. A description of software tools for calculation, measuring, etc., which are useful for the solution

of the tasks, might also be included.

Training notes for the trainer / instructor

The trainer / instructor notes provide further recommendations, suggestions and information to

professionally execute the training and support students effectively in their learning.

© Festo Didactic GmbH & Co. KG 8027890 1




1.1.1 System data _______________________________________________________________________ 3





1.4.1 Pre-treatment ______________________________________________________________________ 7




2 Sedimentation ___________________________________________________________________ 10

2.1 Fundamentals ____________________________________________________________________ 10










2.2 Exercises ________________________________________________________________________ 25






3.1 Fundamentals ____________________________________________________________________ 34

3.1.1 Aerobic wastewater treatment _______________________________________________________ 34

3.1.2 Terms to characterize the activated sludge process ______________________________________ 36

3.2 Exercises ________________________________________________________________________ 37


3.2.2 Aeration _________________________________________________________________________ 41

Appendix ______________________________________________________________________________ 48


Components ____________________________________________________________________________ 50

Abbreviations ___________________________________________________________________________ 53


2 © Festo Didactic GmbH & Co. KG 8027890


1 Wastewater treatment

1.1 The training equipment

The System has been designed for use in the learning modules Wastewater treatment, Monitoring,

controlling and optimising operations and Energy optimisation in water and wastewater treatment plants.

In the learning module “Wastewater treatment”, the system is used to illustrate the principles of wastewater

treatment processes focused on sedimentation, biological treatment and sludge recirculation. In learning

module “Energy optimisation” the system illustrates processes and measures related to energy efficiency in

the water and wastewater treatment, especially aeration.

Picture of the Wastewater Treatment System

1.1.1 System data

Main components

Tank, 3 l Flow sensor

Tank, 10 l Dissolved oxygen sensor (optional accessory)

Aeration Recirculation pump

Overflow edge 2-way solenoid valve

Capacitive proximity sensor I/O interface

Float switch Aluminium profile plate



Dimensions

Width: 710 mm

Depth: 400 mm


Order number of the Wastewater Treatment System: 8024507

1.1.2 Piping and instrumentation diagram of the Wastewater Treatment System

1.2 The most important P&I symbols used for the EDS® Water Management

Piping and Instrumentation (P&I) diagrams show the functional layout of a plant or facility. P&I diagrams

contain different symbols for sensors, valves, actuators, motors, pumps, tanks and pipes. The P&I diagrams

in this workbook are based on EN 62424 respectively EN 10628. To keep the diagrams easy to read, a

simplified form is used.



Symbol Meaning

Pump with electric motor

Tank (sedimentation tank shape)

Filter

Pipe

Branching pipe

Actuator (general symbol)

Manual actuator

Manual valve

Sensor

Top: FIC means flow sensor (F) which shows the current value (I) and can be used

for closed loop control (C)

Bottom: numbering

Further explanation of the characters in the top of the symbol: see table below

Symbols – Examples from the EDS® systems

First character Following character(s)

F Flow A Alarm

L Level C Controller

P Pressure I Instantaneous value

Q Quality O Optical signal

T Temperature R Registration

D Difference +/- Threshold

Denomination of sensors



1.3 Learning outcomes correlated with exercises

With exercise 2.2.1 “Analysis of factors affecting sedimentation” the student can:

name purposes of the sedimentation process

find causes for poor sedimentation and conditions for good sedimentation

list problems which may occur and name corrective actions

With exercise 2.2.2 “Simulation of the sedimentation of sludge (granulate)” the student can:

explain basic processes involved in sedimentation

sketch effects of an excessive (surface) input to a sedimentation tank

describe effects of an excessive concentration of solids in the input to a sedimentation tank .

With exercise 2.2.3 “Analysis of flow rates” the student can:

describe and explain the behaviour of floc (in the exercise granulate) in the tanks under different flow

rates.

With exercise 2.2.4 “Influence of solids load on sedimentation” the student can:

describe the behaviour of granulate with rising concentrations in tank

explain how settleability of particles and particle concentration influence the sedimentation process.

With exercise 3.2.1 “Keeping solids concentration in the aeration tank high” the student can:

describe the basic function of aerobic water treatment and the role of sludge recirculation

explain the significance of sludge recirculation to the aeration tank

name the consequences of hydraulic overload of a wastewater treatment plant.

With exercise 3.2.2 “Aeration” the student can:

explain the basic function of aerobic wastewater treatment using the activated sludge processes

measure and name the amount of oxygen dissolved in water without bubble aeration

describe the significance of oxygen injection into the aeration tank

explain the benefits of constantly measuring dissolved oxygen in an aeration tank.



1.4 Introduction to the learning module “Wastewater treatment”

In nature, water bodies normally have the power to purify themselves due to the presence of certain

microorganisms such as bacteria and algae, which decompose the organic compounds in the wastewater,

breaking and transforming them into simple substances such as carbon dioxide or nitrogen. If the

microorganisms have enough time to decompose organic compounds and consequently keep their

concentrations within certain limits, then the self-purification process does the job. Treatment becomes

necessary as soon as discharge volume and consequently, concentrations rise. In this case, bacteria growth

and the oxygen demand in the water will also increase.

Wastewater treatment accelerates the natural decomposition by optimising the conditions for decomposing

bacteria.

The efficient and economic layout of a wastewater treatment plant requires a careful design based on

aspects such as flow rates, components of the raw wastewater and organic load, end use of the treated

water, economic viability, site area available for installation and climatic patterns as temperature and

rainfall. This is why, there is no standard solution, but the selection of processes and the type of wastewater

treatment plant will vary depending on each specific case. However, the usual process of treating domestic

wastewater can be divided into the following standard stages:

Pre-treatment

Primary or physical treatment

Secondary or biological treatment and

Tertiary treatment usually involving chlorination.

1.4.1 Pre-treatment

This step does not affect dissolved organic material in wastewater. The aim is the separation of very coarse

particles and sandy or easily separable materials whose presence would disrupt the overall treatment and

efficient functioning of machines, equipment and facilities of the treatment plant. The headworks are the

initial receiving area for raw wastewater from the conveyance system. Screens filter out large materials and

grit chambers allow heavy sand and rocks to settle before wastewater is sent to the primary clarifiers. In

addition, there is sieving to eliminate coarse solids in suspension, settling to remove dense sand as well as

a degreasing to get rid of fats, oils, foams and other floating materials lighter than water, which may distort

the subsequent treatment processes.



1.4.2 Primary Treatment

The primary treatment mainly consists of removing suspended flocculent solids by sedimentation or

flocculation, neutralizing the acid and eliminating inorganic material by chemical precipitation. In some

cases coagulation is used to support the sedimentation process. In this workbook special focus is laid upon

sedimentation as primary treatment process.

1.4.3 Secondary or biological treatment

Once passed the pre-treatment and primary treatment stages, the aim of secondary or biological treatment

is to reduce the organic material in the wastewater. Secondary treatment has been designed based on the

biological process of self-purification – mentioned above – which occurs naturally. It helps to prevent water

bodies from being polluted by natural born wastewater.

In the corresponding processes, the biodegradable organic matter from domestic wastewater acts as

nutrient for a bacterial population which is provided with oxygen in controlled conditions. In summary, the

biological treatment, is so to say, an accelerated natural oxidation process were biodegradable organic

matter is decomposed by bacteria. Biological wastewater treatment subsequently avoids the entry of

contaminants which could induce a lack of oxygen in water bodies.

The most common aerobic processes with suspended biomass, are the aerated lagoon and the activated

sludge or aeration tank which is treated in detail in this workbook.



1.4.4 Tertiary treatment

Tertiary treatment goals are to eliminate the remaining organic load of secondary treatment, to remove

pathogenic microorganisms, to eliminate undesired colour and odour and to remove residual detergents,

phosphates and nitrates causing waste foam and eutrophication. Chlorination is part of tertiary or advanced

treatment that is used to achieve purer water, even down to drinkable if desired.

In wastewater treatment it is important to take into account the handling of sludge from the primary and

secondary treatments. These sludges can cause damage to the environment and have to be treated and

discharged in a controlled fashion.

A summary of generic treatments that can be applied to domestic wastewater and industrial wastewater is

represented in this scheme:

Generic wastewater treatment process (basis source:University of Pretoria, Prof. EMN Chirva)


Exercises and worksheets



1.1.1 System data _______________________________________________________________________ 3





1.4.1 Pre-treatment ______________________________________________________________________ 7




2 Sedimentation ___________________________________________________________________ 10

2.1 Fundamentals ____________________________________________________________________ 10




2.1.4 Outlet zone ______________________________________________________________________ 12

2.1.5 Sludge Zone _____________________________________________________________________ 12







2.2 Exercises ________________________________________________________________________ 25






3.1 Fundamentals ____________________________________________________________________ 34

3.1.1 Biological treatment principles ______________________________________________________ 34

3.2 Exercises ________________________________________________________________________ 37


3.2.2 Aeration _________________________________________________________________________ 41

Appendix ______________________________________________________________________________ 48


Components ____________________________________________________________________________ 50

Abbreviations ___________________________________________________________________________ 53

Exercises and worksheets


© Festo Didactic GmbH & Co. KG 8027890 Name: __________________________________ Date: ____________ 3


1.1 The training equipment

The System has been designed for use in the learning modules Wastewater treatment, Monitoring,

controlling and optimising operations and Energy optimisation in water and wastewater treatment plants.

In learning module “Wastewater treatment”, the system is used to illustrate the principles of wastewater

treatment processes focused on sedimentation, biological treatment and sludge recirculation. In learning

module “Energy optimisation” the system illustrates processes and measures related to energy efficiency in

the water and wastewater treatment, especially aeration.

Picture of the Wastewater Treatment System

1.1.1 System data

Main components

Tank, 3 l Flow sensor

Tank, 10 l Dissolved oxygen sensor (optional accessory)

Aeration Recirculation pump

Overflow edge 2-way solenoid valve

Capacitive proximity sensor I/O interface

Float switch Aluminium profile plate


4 Name: __________________________________ Date: ____________ © Festo Didactic GmbH & Co. KG 8027890

Dimensions

Width: 710 mm

Depth: 400 mm


Order number of the Wastewater Treatment System: 8024507

1.1.2 Piping and instrumentation diagram of the Wastewater Treatment System

1.2 The most important P&I symbols used for the EDS® Water Management

Piping and Instrumentation (P&I) diagrams show the functional layout of a plant or facility. P&I diagrams

contain different symbols for sensors, valves, actuators, motors, pumps, tanks and pipes. The P&I diagrams

in this workbook are based on EN 62424 respectively EN 10628. To keep the diagrams easy to read, a

simplified form is used.



Symbol Meaning

Pump with electric motor

Tank (sedimentation tank shape)

Filter

Pipe

Branching pipe

Actuator (general symbol)

Manual actuator

Manual valve

Sensor

Top: FIC means flow sensor (F) which shows the current value (I) and can be used

for closed loop control (C)

Bottom: numbering

Further explanation of the characters in the top of the symbol: see table below

Symbols – Examples from the EDS® systems

First character Following character(s)

F Flow A Alarm

L Level C Controller

P Pressure I Instantaneous value

Q Quality O Optical signal

T Temperature R Registration

D Difference +/- Threshold

Denomination of sensors



1.3 Learning outcomes correlated with exercises

With exercise 2.2.1 “Analysis of factors affecting sedimentation” the student can:

name purposes of the sedimentation process

find causes for poor sedimentation and conditions for good sedimentation

list problems which may occur and name corrective actions

With exercise 2.2.2 “Simulation of the sedimentation of sludge (granulate)” the student can:

explain basic processes involved in sedimentation

sketch effects of an excessive (surface) input to a sedimentation tank

describe effects of an excessive concentration of solids in the input to a sedimentation tank .

With exercise 2.2.3 “Analysis of flow rates” the student can:

describe and explain the behaviour of floc (in the exercise granulate) in the tanks under different flow

rates.

With exercise 2.2.4 “Influence of solids load on sedimentation” the student can:

describe the behaviour of granulate with rising concentrations in tank

explain how settleability of particles and particle concentration influence the sedimentation process.

With exercise 3.2.1 “Keeping solids concentration in the aeration tank high” the student can:

describe the basic function of aerobic water treatment and the role of sludge recirculation

explain the significance of sludge recirculation to the aeration tank

name the consequences of hydraulic overload of a wastewater treatment plant.

With exercise 3.2.2 “Aeration” the student can:

explain the basic function of aerobic wastewater treatment using the activated sludge processes

measure and name the amount of oxygen dissolved in water without bubble aeration

describe the significance of oxygen injection into the aeration tank

explain the benefits of constantly measuring dissolved oxygen in an aeration tank.



1.4 Introduction to the learning module “Wastewater treatment”

In nature, water bodies normally have the power to purify themselves due to the presence of certain

microorganisms such as bacteria and algae, which decompose the organic compounds in the wastewater,

breaking and transforming them into simple substances such as carbon dioxide or nitrogen. If the

microorganisms have enough time to decompose organic compounds and consequently keep their

concentrations within certain limits, then the self-purification process does the job. Treatment becomes

necessary as soon as discharge volume and consequently, concentrations rise. In this case, bacteria growth

and the oxygen demand in the water will also increase.

Wastewater treatment accelerates the natural decomposition by optimising the conditions for decomposing

bacteria.

The efficient and economic layout of a wastewater treatment plant requires a careful design based on

aspects such as flow rates, components of the raw wastewater and organic load, end use of the treated

water, economic viability, site area available for installation and climatic patterns as temperature and

rainfall. This is why, there is no standard solution, but the selection of processes and the type of wastewater

treatment plant will vary depending on each specific case. However, the usual process of treating domestic

wastewater can be divided into the following standard stages:

Pre-treatment

Primary or physical treatment

Secondary or biological treatment and

Tertiary treatment usually involving chlorination.

1.4.1 Pre-treatment

This step does not affect dissolved organic material in wastewater. The aim is the separation of very coarse

particles and sandy or easily separable materials whose presence would disrupt the overall treatment and

efficient functioning of machines, equipment and facilities of the treatment plant. The headworks are the

initial receiving area for raw wastewater from the conveyance system. Screens filter out large materials and

grit chambers allow heavy sand and rocks to settle before wastewater is sent to the primary clarifiers. In

addition, there is sieving to eliminate coarse solids in suspension, settling to remove dense sand as well as

a degreasing to get rid of fats, oils, foams and other floating materials lighter than water, which may distort

the subsequent treatment processes.



1.4.2 Primary Treatment

The primary treatment mainly consists of removing suspended flocculent solids by sedimentation or

flocculation, neutralizing the acid and eliminating inorganic material by chemical precipitation. In some

cases coagulation is used to support the sedimentation process. In this workbook special focus is laid upon

sedimentation as primary treatment process.

1.4.3 Secondary or biological treatment

Once passed the pre-treatment and primary treatment stages, the aim of secondary or biological treatment

is to reduce the organic material in the wastewater. Secondary treatment has been designed based on the

biological process of self-purification – mentioned above – which occurs naturally. It helps to prevent water

bodies from being polluted by natural born wastewater.

In the corresponding processes, the biodegradable organic matter from domestic wastewater acts as

nutrient for a bacterial population which is provided with oxygen in controlled conditions. In summary, the

biological treatment, is so to say, an accelerated natural oxidation process were biodegradable organic

matter is decomposed by bacteria. Biological wastewater treatment subsequently avoids the entry of

contaminants which could induce a lack of oxygen in water bodies.

The most common aerobic processes with suspended biomass, are the aerated lagoon and the activated

sludge or aeration tank which is treated in detail in this workbook.



1.4.4 Tertiary treatment

Tertiary treatment goals are to eliminate the remaining organic load of secondary treatment, to remove

pathogenic microorganisms, to eliminate undesired colour and odour and to remove residual detergents,

phosphates and nitrates causing waste foam and eutrophication. Chlorination is part of tertiary or advanced

treatment that is used to achieve purer water, even down to drinkable if desired.

In wastewater treatment it is important to take into account the handling of sludge from the primary and

secondary treatments. These sludges can cause damage to the environment and have to be treated and

discharged in a controlled fashion.

A summary of generic treatments that can be applied to domestic wastewater and industrial wastewater is

represented in this scheme:

Generic wastewater treatment process (basis source:University of Pretoria, Prof. EMN Chirva)

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